[syslinux] memdisk install check on iso images

[Richard Russo]

I've been able to use the memdisk installation check api on images loaded as a hard drive, but it doesn't seem to work if the image is loaded as an ISO. I'm using the official memdisk binary from the 6.03 release.

This is the api described on the old API page:
	EAX = 454D08xxh ("ME") (08h = parameter query)
	ECX = 444Dxxxxh ("MD")
	EDX = 5349xxnnh	("IS") (nn = drive #)
	EBX = 3F4Bxxxxh ("K?")
	INT 13h

I'm not super familiar with int 13h; is it normal that a cd-rom drive would respond with an error to the 08h parameter query, and that's why it doesn't show up with the install check? In which case, it might be better for me to go through the int 13h safe hook detection?

For context, I'm working on detecting memdisk images in the FreeBSD boot loader, so they can be used by the kernel once booted (which will enable pxebooting installer images).

Thanks!

-- 
  Richard Russo
  toast at ruka.org